1. Field of the Invention
The present invention relates to a semiconductor package, and more particularly, to a semiconductor package wherein the chip is attached to the leadframe.
2. Description of the Prior Art
While the size of periphery of semiconductor chip is decreased, the position of bonding pads must be taken care simultaneously to prevent the supporting bar from contacting with the leadframe, which results in the failure of electronic property. In general, the package with LOC (lead on chip) structure increases the package density and improves the performance. In past, the conventional package includes the leadframe having the die pad for supporting the chip. In the conventional package having the leadframe, as shown in FIG. 1 and FIG. 3, the chip is positioned onto the die pad whose size is larger than that of the chip. To describe the conventional package having leadframe more detail, the chip 20 is attached to the die pad 80 and then electrically coupled to the leadframe 10 by the bonding wires 30 for transmitting signal; the molding compound is used to encapsulate the above leadframe 10 and the chip 20 to form a complete package body that also protect the bonding wires 30 from break resulted from the external force. However, the package body may be broken due to the stress resulted from "the popcorn effect", caused by the evaporated moisture during the under-filling process for injecting the molding compound. To explain "the popcorn effect" more detail, the delamination or gap is liable to form between the die pad and the molding compound due to the poor adhesion. Therefore, the moisture may be absorbed by the delamination or gap within the package body during the storage stage, and then the moisture will be evapored after the package body being moved into the furnace for heating. Thus, the cracks caused by the evaporated moisture will break the package body. One method for solving "the popcorn effect" that cause the cracks is to carry out the baking process, which is executed before the package body moved into the furnace, to remove the moisture. Another method is to form a plurality of through holes, such as heat exhausting holes, to drive out the moisture.